Zr基共晶合金组织结构与力学性能协同优化研究

Study on Synergistic Optimization of Microstructure and Mechanical Properties of Zr-based Eutectic Alloy

摘要:

本文基于共晶合金设计策略结合Pandat热力学计算，设计并制备了Zrx(NiFe)100-x合金（x=75/83/90 wt.%），研究了合金组织结构与力学性能的内在关联机制。结果表明，当Zr含量提升至83 wt.%及以上时，合金呈现片层状共晶组织（tI12-Zr2(Ni/Fe)/FCC-Zr）与HCP-Zr复合结构，界面处析出纳米级FeZr3过渡相，其液相形成温度显著降低至约974℃；83Zr与90Zr合金的抗压强度和断裂应变分别1352±12 MPa、14.2±0.4%和1263±10 MPa、17±0.3%，在保证合金强度的情况下，断裂应变较传统Zr基非晶合金大幅提升。断口分析表明，共晶界面诱导的位错钉扎与剪切带分叉抑制了裂纹扩展，促使Zr含量提升时，合金断裂模式由脆性解理断裂向45°剪切断裂为主导的方式转变。在动态压缩下，83Zr与90Zr合金均呈现应变率硬化效应，并且当应变率超过临界值时，合金均发生韧脆性转变。该研究为Zr基共晶多相合金的强韧化设计及低熔点成型工艺优化提供了依据。

Abstract:

This investigation adopts a strategic approach focusing on low-melting point eutectic alloy design supplemented by thermodynamic calculations of phase diagrams to develop and characterize Zrx(NiFe)100-x alloy systems (x=75/83/90 wt.%). Results demonstrate that at Zr concentrations of 83 wt.% and above, the alloys develop a distinctive lamellar eutectic microstructure (tI12-Zr2(Ni/Fe)/FCC-Zr) coexisting with HCP-Zr, featuring nanoscale FeZr3 interphase precipitates at eutectic interfaces. Notably, the liquidus formation temperature exhibits a substantial reduction to approximately 974℃, successfully achieving the desired low-melting point characteristics. The Zr83(NiFe)17 and Zr90(NiFe)10 alloys exhibit compressive strengths of 1352±12 MPa and 1253±10 MPa with corresponding fracture strains of 14.2±0.4% and 17±0.3%, respectively. These values represent a significant enhancement in fracture strain compared to conventional Zr-based amorphous alloys while maintaining comparable strength properties. Fractographic analysis reveals that dislocation pinning mechanisms and shear band bifurcation phenomena induced by eutectic interfaces effectively impede crack propagation, facilitating a transition in fracture mode from brittle cleavage to 45° shear-dominated failure with increasing Zr content. Under dynamic compression, both 83Zr and 90Zr alloys exhibit a strain rate hardening effect, and when the strain rate exceeds a critical value, the alloys undergo a ductile-to-brittle transition. This research establishes a fundamental framework for the design of low-melting point Zr-based eutectic multiphase alloys.